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Insulation between original structure and Extension?

Insulation between original structure and Extension?


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Old 02-04-21, 11:04 AM
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Insulation between original structure and Extension?

The previous owner put an extension on the house; a family room on the main floor and a masterbathroom on the second floor just above. Both rooms are connected to the family structure through single, standard size doorways.

The extension rooms seem well built and insulated, but they still remain much colder than the main structure of the house.

I suspect that original exterior wall insulation was left in the newly shared wall when the extension was added.

1) When putting on an extension, is it common to remove the original exterior insulation from what will now be the shared wall?
2) could the presence of this insulation explain temperature differences between
 

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02-04-21, 11:49 AM
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Insulation inside a conditioned space now becomes a sound barrier (although not the greatest efficiency) and would have no impact.

My first question would be to look at the heating system, were ducts run to the new rooms, is the size of the system sufficient to handle the additional square footage, is the duct run now the longest thus just not getting to the room?
 
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Old 02-04-21, 11:49 AM
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Insulation inside a conditioned space now becomes a sound barrier (although not the greatest efficiency) and would have no impact.

My first question would be to look at the heating system, were ducts run to the new rooms, is the size of the system sufficient to handle the additional square footage, is the duct run now the longest thus just not getting to the room?
 
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Old 02-04-21, 12:03 PM
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This is a very good example of having a professional quote or at least advise when adding major additions to a home. Many people don't consider the HVAC power system that was sized for the original structure. I would look closer at the insulation that was used on the new sections and consider supplemental heating as a solution.
 
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Old 02-04-21, 02:02 PM
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I didn't want to overdo it with details about the HVAC but the following should answer most the questions/points raised.

First, they certainly did not have an experiment weigh in on the extension for HVAC. That much is clear by how everything operates.

Second, lets see if you can follow what I like to call the frankenstein HVAC.

The first floor:
-First floor kitchen; hotwater powered kickspace heaters, rm is 200 sqft.
-First floor remaining ORIGINAL STRUCTURE is hotwater baseboard. Maybe 1100 sqft total.
-First floor extension is its own 2 ton ac/hydroair unit. Yes, 2 tons for one 200 sqft room. Its like a tornado when the single speed blower comes on.

The extension connects to the main structure via one normal sized pocket door. The rest of the shared wall is the original exterior wall of the house (obviously refinished with sheetrock). Using FLIR gun it seems the extension room is fairly well insulated all around but it does have 3 exterior walls, slab underneath, 4 windows and a glass sliding door (all double paned). Its dedicated hydroair unit is certainly overkill. The problem is, even on mild days, this room will drop 3 degrees in <1hr, constantly cycling the hydroair unit. On cold days, its even quicker. I thought maybe if the original insulation was left in place on the shared wall, it may be preventing any decent heat transfer across the old and new structure and thus stops any kind of temperature equilibrium. Maybe thats flawed thinking and is ignoring the heat loss issue with that room?

Now the second Floor:
-Second floor heat; is a 2.5 ton ac/hydro unit. Maybe 800 sqft total. NOTE; this unit also provides primary AC and supplemental heat to the kitchen and baseboard zones downstairs. So yes, believe it or not, there are ducts that run to 4-5 rooms downstairs as well as the three bedrooms and two bathrooms upstairs. I think it is still well sized for that load; I'll describe the issue more below.

-Second floor extension (the masterbath), gets heat from the hydro air unit covering the upstairs with a 6x12" register. This is more than enough to keep the bathroom comfortable (when there are calls for heat).

The problem with the second floor is the original structure of the house holds temperature well while the master bathroom (the extension), loses heat much more quickly. Thus, the main part of upstairs can hold 68-70 all day, while the bathroom will drop down to the 50s in a matter of hours. Again, the room looks pretty well sealed using a FLIR gun. But it still cools off because the main house never needs that new call for heat.

Hopefully you were able to follow that. If internal insulation isn't having any significant impact than I am guessing its likely high heat loss in the newer construction that is mismatched with the rest the houes. Which is funny since the extension is 20 years old while the original structure (which seems surprisingly well insulated) is from 1928.

Ultimately, this house will need a full hvac redo, unfortunately thats not in the budget right now. But, I am open to any suggestions.



EDIT:
Also, regarding the supplemental heating...

The previous owner put an electric kickspace heater in the bathroom. Works great but nothing like putting a 1500w electric device on the floor of a room with 4 independent water sources that could leak at any time...
 
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Old 02-04-21, 03:47 PM
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which seems surprisingly well insulated
So then lets back up, what is your insulation situation.

As you may well know heat loss is up, out, then down so your ceiling insulation is by far the most important.

So what do you have in new and old sections?
 
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Old 02-04-21, 04:09 PM
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it does have 3 exterior walls, slab underneath, 4 windows and a glass sliding door (all double paned).
This, in addition to the different heating system and thermostat, is why you have a difference in climate from new to preexisting... and why one calls for heat or AC more often. There is a ton of heat loss there compared with other rooms that only have 1 or 2 exterior walls.
 
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Old 02-04-21, 08:42 PM
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I was really hoping there would be simple answer here. I tried to think of every possible explanation and solution that goes short of redoing all the insulation.

Everything definitely points to the rooms being incorrectly insulated and/or under-insulated. My guess is the previous homeowner went with the cheap contractor who didn't plan or do the work properly. You would think that building an extension in new england with so many windows, on slab, and having three exposed walls you would try to get the insulation right.

Some more details. The original structure does not have a room with more than two external walls, upstairs or downstairs. Majority of the original structure is over a 4ft basement. The floor joists are all insulated. The extension is on slab., no clue about the insulated there. The ceiling in the bathroom is tall, probably 12 feet at the maxima. Its a domed room with wood planks lining it. I have no idea what insulation lays above it. Also, the ceiling is insulated between the family room and the masterbath above it. Not sure what the rating was. (I had it opened briefly when I first bought the house and had to remove an exhaust fan from the ceiling).

What should I be looking out for when I inspect the insulation/walls/floors tomorrow? Ill try to identfiy insulation rating; anything else to check?

Also, are there any solutions here other than pulling down the sheetrock and redoing the insulation?

Here is the temp profile of the extension room.

 
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Old 02-04-21, 08:51 PM
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I'm not a big fan of your dropping the temperature to 60-62 F for such long periods. If the air at the thermostat is 60F (or less), all the building materials are far less than that in the winter when its cold out, and are acting like a cold sink, sucking all the energy out as you try to heat it up again. If you "must" drop the thermostat when you aren't home or are asleep or what have you, only drop it a few degrees (max 5F) from room temperature. Because the colder you set the thermostat, the colder your walls, floor, and windows will be / the harder it will be to heat up again.

If you only have it set to 70F for 2.5 hrs or so, its no wonder its cold in that part of the house. Nothing to do with insulation.

One thing you might experiment with is simply running the fan constantly. It should circulate the air from your tall ceilings, and moving air will prevent the windows from getting so cold.
 
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Old 02-04-21, 09:31 PM
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Thanks for the feedback. I try not to set back to far since I know everything cools down and its tough and costly to warm it all back up but maybe i still am?

Here is my current approach for the house:

Upstairs (which includes the upstairs master bathroom) is 70F during the morning when we get up. 67 during the day. (ecobee will drop it to 65 if we dont go upstairs). Then 62 at night

Downstairs kitchen and main structure is 70F during the day and 64F at night.

Family room (the extension room with its own hvac) is 62F at night. 66F during the day. And then goes up to 70F at night when we watch TV after work.

What do you think of these set backs? too much?
 
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Old 02-04-21, 09:47 PM
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That doesn't seem to agree with what your "temp profile of the extension room" says. And yes, 62F is borderline too low, imo. If your desired room temp was 68F it would probably be ok. But an 8F drop is a bit much, and since you are complaining its cold, that kind of proves it.
 
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Old 02-05-21, 07:06 AM
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PArt of the plot I uploaded above shoes my 60F setback, which was when we were away for three days. Here are some plots from Jan 31. It was cold but it is the typical pattern we set for all the zones on a given day. I would appreciate any feedback/thoughts (are my set backs too much or does it seem like heatloss per any one zone is too high etc)


Extension (Family Rm) - Dedicated Hydroair



Original Garage - Now Kitchen - Two hotwater kickspace heaters with blower fans



Original Structure - Hotwater baseboard



Upstairs - Hydroair unit



Looking at those traces, my gut says the upstairs zone is syphoning heat from the downstairs. Also, since it supplements the downstairs zones (there are some vents feeding downstairs which I am guessing it was done to give AC to the original structure downstairs) , the fact that upstairs heat doesnt come on during the dayon means it never gives assistance to the downstairs zones
 

Last edited by pbct2019; 02-05-21 at 07:43 AM.
 

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